Electroferrographic printing process and apparatus therefor



Oct. 21, 1958 Filed Sept. 21, 1955 TON 2,857,290

W. D. BOL EI..EZCTROFERROGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR 2 Sheets-Sheet 1 RECORD CARD DATA SCANNING SlREADING MEANS INVENTOR. WALLIS D. BOLTON AT TORNEY Oct. 21, 1958 Filed Sept. 21, 1955 III I I KIO FORMING LATENT MAGNETIG IMAGE FIG; 2 1

22 DEVELOPING 26 LATENT COMPOSITE 24 IMAGE FIG-.2 c

I 2a FIXING DEVELOPED IMAGE 29 FIG; 22

W. D. BOLTON ELECTROFERROGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR 2 Sheets-Sheet 2 FORMING LATENT 19 ELECTROSTATIC IMAGE TRANSFERING IO DEVELOPED IMAGE 'FIG. 2 d

ERASING LATENT COMPOSITE IMAGE FIG. 2+:

INVENTOR. WALLIS D. BOLTON ATTORNEY ELECTROFERROGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR Wallis D. Bolton, Vestal, N. Y., assignor to International Business Machines Corporation, New York, N. Y., a corporation of New York Application September 21, 1955, Serial No. 535,604

14 Claims. (Cl. 117--17.5)

This invention relates in general to a so-called electroferrographic printing device for producing printed copy by employing magnetic and electrostatic image producing and developing means.

Ferrographic, or ferromagnetographic, printing may be described as a method by which printed and written text, and pictures are reproduced by forming latent magnetic images thereof on thin sheets of permanent-magnetic material, making these images visible by the deposition of tiny colored ferromagnetic particles on said material, and transferring these particles which define the latent magnetic images to a print receiving material. Electrographic printing, particularly the type referred to as xerography, may be defined as a method by which printed and written text, and pictures are reproduced by forming latent electrostatic images on thin sheets or layers of electrically non-conducting, i. e., dielectric, material, making these images visible by the deposition of tiny pigmented triboelectrically charged electroscopic toner particles on the surface of said material, transferring these toner particles to a print receiving material, such as paper for example, and permanently affixing these transferred toner particles onto the said print receiving material whereby the fixed toner images correspond to the latent electrostatic images.

The preferred embodiment of the invention described herein is a so-called electroferrographic printing machine employing in novel combination magnetic and electrostatic printing machine principles to produce by the conjoint action thereof a single composite image consisting of separate latent magnetic and electrostatic images. Furthermore, a novel so-called electroferroscopic toner having the property of triboelectricferromagnetic particles is used to develop the aforesaid composite image.

A broad object of this invention is to provide an electroferrographic printer.

Another broad object of this invention is to provide an improved printing device for producing copies of printed and written text, and pictures.

Another object of this invention is to provide a printing apparatus for producing and developing a single composite latent image consisting of separate latent electrostatic and magnetic images.

In line with the foregoing, a still another object of this invention is to provide an improved pigmented image developing material for developing said composite latent image.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of examples, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 is a somewhat diagrammatic view of an electroferrographic printer.

Figs. 2a-2f depict the steps necessary to produce and United States Patent develop printed copy by electroferrographic methods and apparatus.

ELECTROFERROGRAPHIC PRINCIPLE General description Referring to Fig. 2a, an electroferroplate 10 which consists of a non-conducting insulating layer 11, such as photoconductive amorphous selenium for example, supported by an electrically conductive, magnetizable backing member 12 made of a nickel-cobalt alloy, for example, may first be subjected to a magnetic field 13. This energy field may be passed through a suitable stencil pattern of a type known to persons familiar with this phase of the graphic arts, so that a cross-section of the magnetic field between stencil 14 and the layer 11 depicts the configuration of the pattern in the said stencil. Thus, a latent magnetic image of the pattern will be formed and stored in the magnetizable member 12. Of course, the image defining magnetic field can be formed in a variety of ways, such as by a permanent-magnet stylus for example. The magnetic field of the stylus is concentrated at the point thereof, so that the same can be used for writing and drawing magnetic images. A permanent-magnet rod whose pole is shaped according to the configuration of the image to be stored in the magnetizable member 12, can also be used to form the latent magnetic image. Furthermore, magnetic materials with current carrying coils about them, i. e., 'electromagnets, can also be used in place of a permanent magnet in order to form the latent magnetic images.

After the latent magnetic image of the pattern defined by stencil 14 is stored in magnetizable member 12, the electroferroplate 10 may have a latent electrostatic image formed and stored in non-conducting layer 11 thereof. This may be done in any one of several ways. For example, if the said layer 11 is a photoconductive insulating layer 11, the same may initially be charged positive by an ion-producing unit (not shown) of the type shown and described in Carlson Patent No. 2,588,699 which issued on March 11, 1952, and thereafter, the said posi tively charged photoconductive insulating layer with the conducting backing member 12 electrically grounded may be subjected to-an optical image which can be formed by passing light rays through an opaque-transparent stencil pattern. As a result, a latent electrostatic image corresponding to the pattern will be produced on the photoconductive insulator for the reason that those electrically charge incremental areas of the photoconductive layer onto which light rays are directed, are discharged, whereas those areas not illuminated by the light rays remain charged.

Another way in which to form a latent electrostatic image on non-conducting layer 11, is to direct electrostatic lines of force 17 through an electrostatic image stencil 18 so that a cross-section of the electrostatic field between stencil 18 and the layer 11 will define the configuration of the pattern in stencil 18. Hence, inasmuch as the magnetizable conducting backing member 12 is electrically connected to ground potential by way of wire 19, a latent electrostatic image corresponding to the pattern of stencil 18, will be stored above the latent magnetic image already formed via stencil 14 in magnetizable member 12 in view of the fact that the nonplural Ways indicated, the said electroferroplate with the single composite latent image there-on may be placed in an image developing apparatus which is similar to the one shown and described in Sabel et al. Patent No.

Patented Oct. 21, 1958 3 2,550,724, which issued on May 1, 1951. Referring to Fig. 20, this developing apparatus includes a pair of electroferroplate holding clamps 21 and 22 to fix the electroferroplate in place, within an oscillatable structure 23. This structure 23 is pivotally mounted on a stationary frame upright 24 via a stud 26. Within the oscillatable structure 23, there is a quantity of developer material 27 having a quantity of electroferroscopic toner therein which said toner will be described in detail hereinafter, and which is for the purpose of developing the said composite latent image on electroferrop'late Hence, as the structure 23 is moved in a see-saw manner about stud 26, the said toner in the developer 27 is caused to cascade over the surface of non-conducting layer 11. Due to the fact that the toner particles have ferromagnetic properties and also have a triboelectric charge, the said toner particles are caused to adhere to the surface of layer 11 in a manner to define the single composite latent image.

The developed toner image 28 on electroferroplate 10 which developed image now visibly defines the aforesaid composite latent image, may be moved from the developing structure 23 shown in Fig. 2c, to the toner image transfer station shown in Fig. 2d Where the developed toner image is transferred from electroferroplate 10 onto a-print receiving material 29, such as paper for example. As shown in Fig. 2d, the transfer station includes a manually operated transfer roller 31 of the general type shown and described in c-opending U. S. patent application, Serial No. 419,314, filed by C. J. Fitch on March 29, 1954, now U. S. Patent No. 2,807,233. The positive potential applied to the transfer roller which, in general, comprises an inner-metallic conductive portion 32 and an outer portion 33 of very resilient or yielding material having a high electrical resistance of at least 10 ohms per cubic centimeter as,

for example, a layer of soft conducting rubber, causes the electroferroscopic toner particles to migrate from the surface of insulating layer 11 to the surface of the print receiving material 29. The transfer roller 31 would, of course, be moved the length of the plate 10 so that all of the toner image 28 would be subjected to the positive transfer potential applied to the transfer roller. There are other suitable methods of transfer, one of which includes the use of a corona unit for example.

Thereafter, in order to fix the toner image 28 onto the print receiving material 29, the said developed image may be subjected to heat (see Fig. 22) which is produced by an electrical heater unit 34 of conventional design. It should be pointed out here that it is well known in the electrographic printing art that an electros copic toner image may be fixed to the print receiving material supporting the same by a suitable toner chemical solvent or by pressure. The same is true of an electroferroscopic toner image. However, in whatever way the electroferroscopic toner image 28 is aflixed to the print receiving material 29, the said fixed image thereon corresponds exactly to the afore-mentioned composite latent image which consists of latent electrostatic and magnetic images.

In order to prepare the electroferroplate 10 for another printing or copying operation, the said composite latent image from which toner image 28 had been developed must be removed in preparation for a new composite latent image. This can be partly done by subjecting the latent magnetic image in magnetizable member 12 to a variable magnetic field which may be produced by an erasing electromagnet 36. Of course, any other apparatus suitable for removing the latent magnetic image stored in member 12, may be used. In order to remove the latent electrostatic image in nonconducting layer 11, the said layer may be subjected to light rays 37 if it is a photoconductive material. If the layer is not photoconductive, it can be discharged by using a grounded conductive wiper element 38 which should be moved over the entire surface thereof so as to remove all of the charge. After the latent electrostatic and magnetic images, i. e., the single composite latent image, have been removed, the electroferroplate 10 may be subjected once again to the several steps depicted by Figs. 2a-2c so as to develop a new composite latent image.

In summation, in order to form a single composite latent image consisting of separate latent electrostatic and magnetic images in superposed storage materials or layers, an electroferrographic plate consisting of a layer of non-conducting, or dielectric, material on a magnetizable conductive supporting backing member, is subjected to a configurated magnetic field and a configurated electrostatic field so that a latent image of the magnetic field is stored in the magnetizable member and a latent electrostatic image is stored in the non-conducting material. Thereafter, an electroferroscopic toner having triboelectric and ferromagnetic properties is applied to said composite latent image so as to cause the same to be developed by adhering to the surface of the non-conducting layer of the electroferroplate 10. Subsequently, the single developed toner image is transferred onto a print receiving member, whereon the same is finally affixed to the said member.

AUTOMATIC ELECTROFERROGRAPHIC PRINTER The basic steps whereby electroferrographic printing and copying are effected have been described with reference to Figs. 2a-2f. There will now be described .a continuous-operation electroferrographic printer which may be record card controlled for printing information carried by the source record cards, onto a print receiving paper web. Inasmuch as the record card feeding mechanism and the record card data reading apparatus for controlling the printer, are not per se a part of this invention, the same will not be described in detail herein so as to avoid undue prolixity and unnecessary complexity. Reference may be had, however, to the copending U. S. patent application, Serial No. 419,392, which was filed by Ira M. Hix et al. on March 29, 1954, for a showing and description of suitable record card handling and scanning equipment.

Referring to Fig. 1, the cylinder 46 of the electroferrographic drum 47 is mounted for rotation on electrically grounded shaft 48, and is driven by an electric mot-or (not shown) in a counterclockwise direction. This drum has secured thereto an electroferroplate 49 which consists of a photoconductive insulating layer 51, such as amorphous selenium for example, supported on an electrically conductive magnetizable backing member 52 made of a nickel-cobalt all-0y, for example. The said electroferroplate 49 is flexed around cylinder 46 as shown, and may be attached thereto in any one of several conventional ways of attaching a printing plate to a supporting cylinder, such as by clamping devices for example. Inasmuch as the insulating layer 51 is a photo-conductive material, it is important that the backing member 52 be in good electrical contact with the electrically grounded drum cylinder 46.

As successive incremental surface areas of the photoconductive insulating layer 51 are moved past ionproducing unit 53 of the type shown and described in Carlson Patent No. 2,588,699 which issued on March 11, 1952, the aforesaid layer 51 is electrically charged positive. These positively charged incremental areas are then moved past an optical image producing unit 54 which projects optical images of the matter to be printed or copied, onto the positively charged surface of photoconductive insulating layer 51. As is shown in Fig. l. the said optical unit 54 is associated with a record card scanning means identified by block 56, and which means are shown and described in detail in the aforementioned copending Hix et al. patent application. Briefly, however, source record cards having information thereon to be copied, are fed, one-by-one, each card cycle operation out of a hopper towards a stacker by successive pairs of feed rolls arranged therebetween. Hence, every record card is caused to be advanced during successive card cycles past a record card data reading station and a record card information optical scanning station. Associated with the optical scanning station may be a single light ray projector for directing a band of light rays upon the constricted center of an aperture past which the information on the record cards to be transferred, is moved. As a result, there is effected a conventional light scanning operation whereby the image of the information printed on the source record cards is transferred via the optical unit 54 onto the charged surface of photoconductive layer 51. Of course, the feeding of the record cards is done at a speed which is correlated to the peripheral speed of the electroferrographic drum 47 so that a good image transfer occurs. Needless to say, there are other modes of optical projection, such as the one shown and described in Butterfield Patent No. 2,641,997 which issued on June 16, I953.

Consequent upon the exposure of the photoconductive layer 51 of electroferroplate 49 to the optical image projected from unit 54, a latent electrostatic image thereof is produced in the said photoconductive insulating layer for the reason that those electrically charged incremental areas of the photoconductive plate onto which light rays are directed, are discharged, whereas those areas not illuminated by light rays remain charged. Hence, after the electroferroplate 49 is exposed to the optical image produced by unit 54, a positively charged latent electrostatic image corresponding to the information carried by the source record cards will be stored in electroferroplate 49.

Continued rotation of the drum 47 in a counterclockwise direction, will move incremental areas of electroferroplate 49 past a magnetic recording head 57. The apparatus associated with the recording head for governing the same may be record card controlled so that a marking magnetic field is directed from the head ont-o electroferroplate 49 at select record card times. As explained previously in connection with Fig. 2, the magnetic fields produced by the recording head 57 will be stored in the magnetizable member 52. Since it is not important as far as this invention is concerned just'how the magnetic fields to be stored are produced, but instead it is important as regards this invention that they are directed onto the electroferroplate 49 for storage, the apparatus for producing the magnetic fields will not be described. There are several practical reasons for making it desirable to have a marking spot, or hit, accompany information to be transferred, one being a change of toner designation in an address label printer of the type disclosed in the aforementioned Hix et al. application. None of these need be covered here, however, in view of the fact that so far as the present invention is concerned, it is only important to have a latent magnetic image stored in a portion of electroferroplate 49 which is related to the area thereof whereat an associated latent electrostatic image is also stored.

Continued rotation of the drum 4'] will cause the composite latent images each consisting of the latent electrostatic and magnetic images to be moved into a developing chamber 58 which may be constructed similarly to the one employed in the printing apparatus disclosed in Schaffert Patent No. 2,576,047 which issued on November 20, 1951. The developing chamber is used to cause the developer material having electroferroscopic toner therein of the type to be described in detail hereinafter, to cascade over the surface of the photoconductive insulating layer 51, and, of course, over the composite latent image in electroferroplate 49. In view of the fact that this toner is comprised of ferromagnetic particles which have a negative triboelectric charge imparted there to by the positive granular carrier particles, the toner will adhere to those areas of the surface of layer 51 which correspond to, and actually define, the composite latent image. Thus, a toner image which visibly defines the composite latent image is developed on the surface of insulating layer 51 of electroferroplate 49. Of course, the carrier in the developer as well as surplus toner that does not adhere to the surface of photoconductive layer 51, will fall into a suitable receiving receptacle within the chamber 58.

A still further counterclockwise rotation of the drum 47 will cause the toner image on electroferroplate 49 to move out of developing chamber 58 and into the realm of a negative ion-producing unit 59 which is similar to unit 53. The effect of the electrostatic field produced by unit 59 is to somewhat decrease the magnitude of the positive latent electrostatic image stored in nonconducting layer 51, so as to thereby condition the toner image being carried by the drum on electroferroplate 49, for transfer onto the print receiving paper web 61. In addition thereto, the negative field to which the photo-conductive layer 51 is subjected, tends to prevent the formation of the undesirable condition selenium fatigue.

Further rotation of the drum 47 causes the toner image to move into a toner transfer, or printing, station whereat a transfer roller 62 similar to roller 31 (Fig. 2d); i. e., one comprising an inner-metallic conductive portion 63 and an outer portion 64 of very resilient o-r yielding material having a high electrical resistance of at least 10 ohms per cubic centimeter, is used to transfer the toner image from electroferroplate 49 onto the surface of print receiving paper web 61. The print receiving paper web 61 is advanced from a web supply roll 66 to a web takeup roll 67 via the afore-mentioned transfer station whereat transfer roll 62 is located, and a pressure fixing station 68. The positive potential applied to the transfer roller causes the electroferroscopic toner particles which define the composite latent image, to migrate from the surface of electroferroplate 49 to the surface of the print receiving paper web which is, of course, advanced at a lineal speed corresponding to the peripheral speed of drum 47.

The transfer might also be effected by magnetic means, such as a permanent magnet roller in place of transfer roller 62 for example. In order to erase the composite latent image from electroferrographic plate 49, light rays from a source 69 and a variable magnetic field produced by an erase head 71 of conventional design, are directed towards the electroferroplate 49. As explained previously in connection with Fig. 2f, the light rays will discharge the photoconductive layer 51 so as to erase the latent electrostatic image therefrom, whereas the variable magnetic field will erase the latent magnetic image stored in magnetizable backing member 52. Either latent image might be erased alone, of course, by operating only one erasing means. In order to remove any excess electroferroscopic toner particles that might remain on the surface of electroferroplate 49 after toner image transfer but prior to electrically charging the incremental surface areas of photoconductive insulating layer 51 again by ionproducing unit 53 during another machine cycle, a rotating plush cleaning roller 72 is provided. This cleaning roller is positioned within a housing 73 for retaining the toner removed from the surface of said plate by the action of said cleaning roller on the surface of plate 49. A vacuum cleaner unit (not shown) may also be utilized within the housing 73 in order to remove the toner accumulated therein.

Pressure fixing rollers 74 and 76 are employed to fix the toner images which are transferred onto the surface of print receiving web 61. A sulficient line contact pres sure of approximately 500 pounds per lineal inch of contact will cause the toner supported by the surface of the paper web 61 to flow into the fibers thereof so as to provide a permanent image. In order that the web 61 transfer rollers 74 and 76 under high pressure, the said rollers are connected to the main drive mechanism so as to be rotated in step with the electroferrographic drum 47. An oil pad 77 may be provided to remove any excess toner which clings to the fixing roller 74.

ELECTR OFERROSCOPIC TONER As stated previously, the preferred embodiment of this invention is an electroferrographic printer whereby a latent composite image consisting of latent electrostatic and magnetic images formed and stored in superposed materials, is produced and developed. This latent composite image is developed by applying a developer material having electroferroscopic toner therein which is comprised of particles having'ferromagnetic and triboelectric properties.

The make-up and the physical and electrical properties of electroscopic, or xerographic, toner suitable for developing latent electrostatic images, are described in Copley Patent No. 2,659,670 which issued on November 17, 1953 and Walkup et al. Patent No. 2,638,416 which issued on May 12, 1953. Furthermore, an electroscopic developer material which consists of electroscopic toner particles and triboelectrically opposite granularcarrier particles, is described in said Walkup et al. patent. As is brought out therein, the materials for the electroscopic toner and the granular carrier, are selected in accordance with their triboelectric properties so that when mixed or brought into mutual contact, one material, e. g., the carrier, is charged positive if the other material is below it in a triboelectric series, and negative, e. g., the toner, if the other material is above it in a triboelectric series; The carrier particles may be of a size in the order of 30 to 60 mesh, and may be comprised of a non-magnetic core having a coating bonded thereto which is triboelectrically opposite to the toner particles. The size of the carrier particles is such that the granular carrier particles will flow easily over the electroferroplate by gravity. In addition, the specific gravity of the carrier particles is higher than that for the toner particles so that the former will not adhere to the surface whereon the latent magnetic and electrostatic images are formed. The core of each carrier particle is non-magnetic, of course, so as not to be attractable to a latent magnetic image. The electroscopic toner which may have different compositions, is a very fine powder, usually made up as a resin base material, and sometimes includes more or less of a material which is in the class of a plasticizer for the resin. It also usually contains a dye or pigment for color imparting purposes.

In view of the fact that the latent electrostatic image produced by the preferred embodiment of this invention, is a positive image, the electroscopic toner and carrier therefor are such that the said toner particles are charged negative by the triboelectric action. It has been found that by mixing one part iron powder of the type known commercially as GAP carbonyl iron (produced by General Aniline and Film Corporation), for instance, with two parts, by weight, of electroscopic toner known experimentally as BXT-75 and commercially as P3 (produced by The Haloid Company), for example, a so-called electroferroscopic toner suitable for developing latent composite images of the type described herein, is produced.

This latter toner may be manufactured by first melting the electroscopic toner with the iron powder, and then deagglomerating the resolidified mass thereof to toner particles having a 2 to 20 micron size. Another satisfactory electroferroscopic toner can be produced by coating ferromagnetic particles with a layer of the electroscopic toner material having triboelectric properties.

It should be apparent that the electroferrographic toner may be used to develop either a latent electrostatic image or a latent magnetic image; there need not necessarily be a latent composite image.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope-of the following claims.

What is claimed is:

1. In a printing device of the class described including a layer of non-conducting insulating material supported by a layer of magnetizable material, the combination of means for forming a latent magnetic image in said magnetizable material, means for forming a latent electrostatic image in said non-conducting insulating material, and means for developing said latent images simultaneously on the exposed surface of said non-conducting,insulating material by applying thereto a pigmented powder having ferromagnetic and triboelectric properties.

2. In an electroferrographic transfer device. of the class described for transferring onto a copy sheet a pigmented powder having electrostatic and magnetic properties, said transfer device including a layer of non-conducting insulating material contiguously supported by a layer of magnetizable material, the combination of means for forming a latent magnetic image in said magnetizable material, means for forming a latent electrostatic image in said non-conducting insulating material, means including pigmented powder dispensing means for developing said latent images simultaneously on the exposed surface of said non-conducting insulating material, and means for simultaneously transferring onto said copy sheet said developed powder images corresponding to said latent images, to thereby form a single composite pigmented powder image on said copy sheet.

3. A device according to claim 2 additionally comprising means for affixing said single composite pigmented powder image onto said copy sheet.

4. A device according to claim 2 additionally comprising means for erasing said latent electrostatic and magnetic images selectively after the transfer of said developed pigmented powder images to said copy sheet.

5. A device according to claim 2 additionally comprising means for erasing said latent electrostatic and magnetic images after the transfer of said developed pig mented powder images to said copy sheet.

6. In an electroferrographic printer of the class described for transferring onto a copy sheet a pigmented developing powder having electrostatic and magnetic properties, said printer including an electroferroplate having a layer of non-conducting material supported by a layer of electrically conductive magnetizable material, the combination of means for forming a latent magnetic image in said magnetizable material, means for forming a latent electrostatic image in said insulating material so that said latent electrostatic and said latent magnetic images are in superposed relation to thereby define a latent composite image in said electroferrographic plate, means for developing said latent composite image by applying said pigmented developing powder to said electroferroplate, and electrostatic field producing meansfor transferring said developed image onto said copy sheet.

7. An electroferrographic printer of the class described for transferring onto a copy sheet an electroferroscopic powder image of a composite object to be copied, comprising an electroferroplate having a layer of dielectric material contiguously supported by a layer of electrically conductive magnetizable material, a magnetic field'image producing means for directing a magnetic field image of a first object onto said electroferroplate so as to store-a latent magnetic image of said first object therein, electrostatic field image producing means for directing an electrostatic field image of asecond object onto said electroferroplate so as to store a latent electrostatic image of said second object therein, whereby a latent composite image is. stored in said electroferroplate, means for applying electroferroscopic toner powder having ferromagnetic and triboelectric properties to the exposed surface of said dielectric material so as to develop said latent composite image, and magnetic field producing means for transferring said developed composite image onto said copy sheet.

8. An electrophotoferrographic printer of the class described for transferring onto a copy sheet an electroferroscopic toner powder image, comprising an electroferroplate having a layer of photoconductive insulating material contiguously supported on an electrically conductive magnetizable member, magnetic field image producing means for directing a magnetic field image of a first object onto said electroferroplate so as to store a latent magnetic image .of said first object in said member, electrostatic field producing means for charging said photoconductive insulating material, optical image producing means for projecting an optical image of a second object onto said charged photoconductive insulating material so that a corresponding latent electrostatic image of said second object is formed in said photoconductive insulating material, means for applying electroferroscopic toner powder having ferromagnetic and triboelectric properties to the exposed surface of said photoconductive insulating material so as to develop said latent images simultaneously, and electrostatic field producing means for transferring said developed toner images simultaneously onto said copy sheet, to thereby form a single electroferroscopic toner image on said copy sheet.

9. An electrophotoferrographic printer according to claim 8 additionally comprising light energy producing means for erasing only said latent electrostatic image after said developed images have been transferred onto said copy sheet.

10. A method of printing an electroferroscopic powder developed image from an electroferroplate having a photoeonductive insulating layer supported by a conducting magnetizable member onto the surface of a print receiving material, which includes the steps of producing a composite latent image on said electroferroplate by forming and storing a latent magnetic image of a first object in the magnetizable member of said electroferroplate and a latent electrostatic image of a second object in the insulating layer thereof, developing said composite latent image by applying electroferroscopic powder to the exposed surface of the insulating layer of said electroferro- 10 plate, transferring said electroferroscopic powder developed composite latent image from said electroferroplate onto the surface of the print receiving material, and permanently affixing said transferred electroferroscopic powder image to said print receiving material.

11. The process of claim 10 wherein said transferred electroferroscopic powder developed composite latent image is permanently aifixed to said print receiving material by heat energy.

12. The process of claim 10 wherein said electroferroscopic toner powder includes two to twenty micron particles each of which is a mixture of one part carbonyl iron powder and two parts electroscopic toner powder.

13. The process of claim 10 wherein the photoconductive insulating layer of said electroferroplate is composed of photoconductive amorphous selenium.

14. A method of printing an electroferroscopic powder developed image from an electroferroplate having an insulating layer supported by a conducting magnetizable member onto the surface of a print receiving material, which includes the steps of producing a composite latent image in said electroferroplate by forming and storing a latent magnetic image of a first object in the magnetizable member of said electroferroplate and a latent electrostatic image of a second object in the insulating layer thereof,

and developing said composite latent image by applying electroferroscopic powder to the exposed surface of the insulating layer of said electroferroplate.

References Cited in the file of this patent UNITED STATES PATENTS 2,618,551 Walkup Nov. 18, 1952 2,624,652 Carlson Jan. 6, 1953 2,726,166 Greaves Dec. 6, 1955 OTHER REFERENCES Berry et al.: Ferromagnetography-High Speed,"

General Electric Review, July 1952, pp. 20, 21, 22 and 61.

Young et al.: Electrofax. Reprint from R. C. A. Review, Dec. 1954, vol. XV, No. 4, pp. 471, 472, 480 and 481.

Atkinson et al.: Journal of The Franklin Institute, vol.

252, Nov. 1951, No. 5, pp. 373-381. 

10. A METHOD OF PRINTING AN ELECTROFERROSCOPIC POWDER DEVELOPED IMAGE FROM AN ELECTROFERROPLATE HAVING A PHOTOCONDUCTIVE INSULATING LAYER SUPPORTED BY A CONDUCTING MAGNETZABLE MEMBER ONTO THE SURFACE OF A PRINT RECEIVING MATERIAL, WHICH INCLUDES THE STEPS OF PRODUCING A COMPOSITE LATENT IMAGE ON SAID ELECTROFERROPLATE BY FORMING AND STORING A LATENT MAGNETIC IMAGE OF A FIRST OBJECT IN THE MAGNETIZABLE MEMBER OF SAID ELECTROFERROPLATE AND A LATEN ELECTROSTATIC IMAGE OF A SECOND OBJECT IN THE INSULATING LAYER THEREOF, DEVELOPING SAID COMPOSITE LATENT IMAGE BY APPLYING ELECTROFERROSCOPIC POWDER TO THE EXPOSED SURFACE OF THE INSULATING LAYER OF SAID ELECTROFERROPLATE, TRANSFERRING SAID ELECTROFERROSCOPIC POWDER DEVELOPED COMPOSITE LATENT IMAGE FROM SAID ELECTROFERROPLATE ONTO THE SURFACE OF THE PRINT RECEIVING MATERIAL, AND PERMANENTLY AFFIXING SAID TRANSFERRED ELECTROFERROSCOPIC POWDER IMAGE TO SAID PRINT RECEIVING MATERIAL. 